A Medley of Potpourri

Tuesday, February 19, 2019

Jet Propulsion Laboratory

From Wikipedia, the free encyclopedia

**Jet Propulsion Laboratory**
Agency overview


Aerial view of JPL
Formed	October 31, 1936; 82 years ago
Jurisdiction	Federal government of the United States
Headquarters	4800 Oak Grove Drive, Pasadena, California, U.S. 34°12′6.1″N 118°10′18″WCoordinates: 34°12′6.1″N 118°10′18″W
Employees	g.t. 6,000
Agency executive	Michael M. Watkins, Director
Parent agency	Managed for NASA by Caltech
Child agency	JPL Science Division
Website	JPL home page

The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in La Cañada Flintridge, California, United States, though it is often referred to as residing in Pasadena, California, because it has a Pasadena ZIP Code.

Founded in the 1930s, the JPL is currently owned by NASA and managed by the nearby California Institute of Technology (Caltech) for NASA. The laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA's Deep Space Network.

Among the laboratory's major active projects are the Mars Science Laboratory mission (which includes the Curiosity rover), the Mars Reconnaissance Orbiter, the Juno spacecraft orbiting Jupiter, the NuSTAR X-ray telescope, the SMAP satellite for earth surface soil moisture monitoring, and the Spitzer Space Telescope. It is also responsible for managing the JPL Small-Body Database, and provides physical data and lists of publications for all known small Solar System bodies.

The JPL's Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks.

History

The control room at JPL

JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology (GALCIT) when the first set of rocket experiments were carried out in the Arroyo Seco. Caltech graduate students Frank Malina, Qian Xuesen, Weld Arnold, and Apollo M. O. Smith, along with Jack Parsons and Edward S. Forman, tested a small, alcohol-fueled motor to gather data for Malina's graduate thesis. Malina's thesis advisor was engineer/aerodynamicist Theodore von Kármán, who eventually arranged for U.S. Army financial support for this "GALCIT Rocket Project" in 1939. In 1941, Malina, Parsons, Forman, Martin Summerfield, and pilot Homer Bushey demonstrated the first jet-assisted takeoff (JATO) rockets to the Army. In 1943, von Kármán, Malina, Parsons, and Forman established the Aerojet Corporation to manufacture JATO rockets. The project took on the name Jet Propulsion Laboratory in November 1943, formally becoming an Army facility operated under contract by the university.

During JPL's Army years, the laboratory developed two deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate-range ballistic missiles. These missiles were the first US ballistic missiles developed at JPL. It also developed a number of other weapons system prototypes, such as the Loki anti-aircraft missile system, and the forerunner of the Aerobee sounding rocket. At various times, it carried out rocket testing at the White Sands Proving Ground, Edwards Air Force Base, and Goldstone, California.

In 1954, JPL teamed up with Wernher von Braun's engineers at the Army Ballistic Missile Agency's Redstone Arsenal in Huntsville, Alabama, to propose orbiting a satellite during the International Geophysical Year. The team lost that proposal to Project Vanguard, and instead embarked on a classified project to demonstrate ablative re-entry technology using a Jupiter-C rocket. They carried out three successful sub-orbital flights in 1956 and 1957. Using a spare Juno I (a modified Jupiter-C with a fourth stage), the two organizations then launched the United States' first satellite, Explorer 1, on January 31, 1958.

MSL mockup compared with the Mars Exploration Rover and Sojourner rover by the Jet Propulsion Laboratory on May 12, 2008

JPL was transferred to NASA in December 1958, becoming the agency's primary planetary spacecraft center. JPL engineers designed and operated Ranger and Surveyor missions to the Moon that prepared the way for Apollo. JPL also led the way in interplanetary exploration with the Mariner missions to Venus, Mars, and Mercury. In 1998, JPL opened the Near-Earth Object Program Office for NASA. As of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earth's orbit.

JPL was early to employ female mathematicians. In the 1940s and 1950s, using mechanical calculators, women in an all-female computations group performed trajectory calculations. In 1961, JPL hired Dana Ulery as the first female engineer to work alongside male engineers as part of the Ranger and Mariner mission tracking teams.

JPL has been recognized four times by the Space Foundation: with the Douglas S. Morrow Public Outreach Award, which is given annually to an individual or organization that has made significant contributions to public awareness of space programs, in 1998; and with the John L. "Jack" Swigert, Jr., Award for Space Exploration on three occasions – in 2009 (as part of NASA's Phoenix Mars Lander Team), 2006 and 2005.

Location

Research rockets on display at JPL.

When it was founded, JPL's site was immediately west of a rocky flood-plain – the Arroyo Seco riverbed – above the Devil's Gate dam in the northwestern panhandle of the city of Pasadena. While the first few buildings were constructed in land bought from the city of Pasadena, subsequent buildings were constructed in neighboring unincorporated land that later became part of La Cañada Flintridge. Nowadays, most of the 177 acres (72 ha) of the U.S. federal government-owned NASA property that makes up the JPL campus is located in La Cañada Flintridge. Despite this, JPL still uses a Pasadena address (4800 Oak Grove Drive, Pasadena, CA 91109) as its official mailing address. The city of La Cañada Flintridge was incorporated in 1976, well after JPL attained international recognition as a Pasadena institution. There has been occasional rivalry between the two cities over the issue of which one should be mentioned in the media as the home of the laboratory.

Employees

A 1960s advert reads: "When you were a kid, science fiction gave you a sense of wonder. Now you feel the same just by going to work."

There are approximately 6,000 full-time Caltech employees, and typically a few thousand additional contractors working on any given day. NASA also has a resident office at the facility staffed by federal managers who oversee JPL's activities and work for NASA. There are also some Caltech graduate students, college student interns and co-op students.

Education

The JPL Education Office serves educators and students by providing them with activities, resources, materials and opportunities tied to NASA missions and science. The mission of its programs is to introduce and further students' interest in pursuing STEM (science, technology, engineering and mathematics) careers.

Internships and fellowships

JPL offers research, internship and fellowship opportunities in the summer and throughout the year to high school through postdoctoral and faculty students. (In most cases, students must be U.S. citizens or legal permanent residents to apply, although foreign nationals studying at U.S. universities are eligible for limited programs.) Interns are sponsored through NASA programs, university partnerships and JPL mentors for research opportunities at the laboratory in areas including technology, robotics, planetary science, aerospace engineering, and astrophysics.

In August 2013, JPL was named one of "The 10 Most Awesome College Labs of 2013" by Popular Science, which noted that about 100 students who intern at the laboratory are considered for permanent jobs at JPL after they graduate.

The JPL Education Office also hosts the Planetary Science Summer School (PSSS), an annual week-long workshop for graduate and postdoctoral students. The program involves a one-week team design exercise developing an early mission concept study, working with JPL's Advanced Projects Design Team ("Team X") and other concurrent engineering teams.

Museum Alliance

JPL created the NASA Museum Alliance in 2003 out of a desire to provide museums, planetariums, visitor centers and other kinds of informal educators with exhibit materials, professional development and information related to the then-upcoming landings of the Mars rovers Spirit and Opportunity. The Alliance now has more than 500 members, who get access to NASA displays, models, educational workshops and networking opportunities through the program. Staff at educational organizations that meet the Museum Alliance requirements can register to participate online.

The Museum Alliance is a subset of the JPL Education Office's Informal Education group, which also serves after-school and summer programs, parents and other kinds of informal educators.

Educator Resource Center

The NASA/JPL Educator Resource Center, which is moving from its location at the Indian Hill Mall in Pomona, Calif. at the end of 2013, offers resources, materials and free workshops for formal and informal educators covering science, technology, engineering and science topics related to NASA missions and science.

Open house

A display at the May 19, 2007 Open House

The lab had an open house once a year on a Saturday and Sunday in May or June, when the public was invited to tour the facilities and see live demonstrations of JPL science and technology. More limited private tours are also available throughout the year if scheduled well in advance. Thousands of schoolchildren from Southern California and elsewhere visit the lab every year. Due to federal spending cuts mandated by budget sequestration, the open house has been previously cancelled. JPL open house for 2014 was October 11 and 12 and 2015 was October 10 and 11. Starting from 2016, JPL replaced the annual Open House with "Ticket to Explore JPL", which features the same exhibits but requires tickets and advance reservation. Roboticist and Mars rover driver Vandi Verma frequently acts as science communicator at open house type events to encourage children (and particularly girls) into STEM careers.

Other works

In addition to its government work, JPL has also assisted the nearby motion picture and television industries, by advising them about scientific accuracy in their productions. Science fiction shows advised by JPL include Babylon 5 and its sequel series, Crusade.

JPL also works with the Department of Homeland Security Science and Technology Directorate (DHSSTD). JPL and DHSSTD developed a search and rescue tool for first responders called FINDER. First responders can use FINDER to locate people still alive who are buried in rubble after a disaster or terrorist attack. FINDER uses microwave radar to detect breathing and pulses.

Funding

JPL is a federally funded research and development center (FFRDC) managed and operated by Caltech under a contract from NASA. In fiscal year 2012, the laboratory's budget was slightly under $1.5 billion, with the largest share going to Earth Science and Technology development.

Peanuts tradition

There is a tradition at JPL to eat "good luck peanuts" before critical mission events, such as orbital insertions or landings. As the story goes, after the Ranger program had experienced failure after failure during the 1960s, the first successful Ranger mission to impact the Moon occurred after a JPL staff member had decided to pass out peanuts to relieve tension. The staff jokingly decided that the peanuts must have been a good luck charm, and the tradition persisted.

Missions

These are some of the missions partially sponsored by JPL:

List of directors

Theodore von Kármán, 1938 – 1944
Frank Malina, 1944 – 1946
Louis Dunn, 1946 – October 1, 1954
William Hayward Pickering, October 1, 1954 – March 31, 1976
Bruce C. Murray, April 1, 1976 – June 30, 1982
Lew Allen, Jr., July 22, 1982 – December 31, 1990
Edward C. Stone, January 1, 1991 – April 30, 2001
Charles Elachi, May 1, 2001 – June 30, 2016
Michael M. Watkins, July 1, 2016 – ?

Team X

The JPL Advanced Projects Design Team, also known as Team X, is an interdisciplinary team of engineers that utilizes "concurrent engineering methodologies to complete rapid design, analysis and evaluation of mission concept designs".

Controversies

Employee background check lawsuit

On February 25, 2005, Homeland Security Presidential Directive 12 was approved by the Secretary of Commerce. This was followed by Federal Information Processing Standards 201 (FIPS 201), which specified how the federal government should implement personal identity verification. These specifications led to a need for rebadging to meet the updated requirements.

On August 30, 2007, a group of JPL employees filed suit in federal court against NASA, Caltech, and the Department of Commerce, claiming their constitutional rights were being violated by the new, overly invasive background investigations. 97% of JPL employees were classified at the low-risk level and would be subjected to the same clearance procedures as those obtaining moderate/high risk clearance. Under HSPD 12 and FIPS 201, investigators have the right to obtain any information on employees, which includes questioning acquaintances on the status of the employee's mental, emotional, and financial stability. Additionally, if employees depart JPL before the end of the two-year validity of the background check, no investigation ability is terminated; former employees can still be legally monitored.

Employees were told that if they did not sign an unlimited waiver of privacy, they would be deemed to have "voluntarily resigned". The United States Court of Appeals for the Ninth Circuit found the process violated the employees' privacy rights and issued a preliminary injunction. NASA appealed and the US Supreme Court granted certiorari on March 8, 2010. On January 19, 2011, the Supreme Court overturned the Ninth Circuit decision, ruling that the background checks did not violate any constitutional privacy right that the employees may have had.

Coppedge v Jet Propulsion Laboratory

On March 12, 2012, the Los Angeles Superior Court took opening statements on the case in which former JPL employee David Coppedge brought suit against the lab due to workplace discrimination and wrongful termination. In the suit, Coppedge alleges that he first lost his "team lead" status on JPL's Cassini-Huygens mission in 2009 and then was fired in 2011 because of his evangelical Christian beliefs and specifically his belief in intelligent design. Conversely, JPL, through the Caltech lawyers representing the laboratory, allege that Coppedge's termination was simply due to budget cuts and his demotion from team lead was because of harassment complaints and from on-going conflicts with his co-workers. Superior Court Judge Ernest Hiroshige issued a final ruling in favor of JPL on January 16, 2013.

Pleiades (updated)

From Wikipedia, the free encyclopedia

Pleiades
A color-composite image of the Pleiades from the Digitized Sky Survey Credit: NASA/ESA/AURA/Caltech
Observation data (J2000 epoch)
Constellation	Taurus
Right ascension	03^h 47^m 24^s
Declination	+24° 07′ 00″
Distance	444 ly on average (136.2±1.2 pc)
Apparent magnitude (V)	1.6
Apparent dimensions (V)	110' (arcmin)
Physical characteristics
Other designations	M45, Seven Sisters, Melotte 22

The Pleiades, also known as the Seven Sisters and Messier 45, are an open star cluster containing middle-aged, hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky.

The cluster is dominated by hot blue and luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars were once thought to be left over material from the formation of the cluster, but are now considered likely to be an unrelated dust cloud in the interstellar medium through which the stars are currently passing.

Computer simulations have shown that the Pleiades were probably formed from a compact configuration that resembled the Orion Nebula. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.

Origin of name

The name of the Pleiades comes from Ancient Greek. It probably derives from plein ("to sail") because of the cluster's importance in delimiting the sailing season in the Mediterranean Sea: "the season of navigation began with their heliacal rising". However, in mythology the name was used for the Pleiades, seven divine sisters, the name supposedly deriving from that of their mother Pleione and effectively meaning "daughters of Pleione". In reality, the name of the star cluster almost certainly came first, and Pleione was invented to explain it.

Folklore and mythology

The Nebra sky disk, dated circa 1600 BC. The cluster of dots in the upper right portion of the disk is believed to be the Pleiades.

The Pleiades are a prominent sight in winter in the Northern Hemisphere, and are easily visible out to mid-Southern latitudes. They have been known since antiquity to cultures all around the world, including the Celts, Hawaiians (who call them Makaliʻi ), Māori (who call them Matariki), Aboriginal Australians (from several traditions), the Persians, the Arabs (who called them Thurayya ), the Chinese (who called them 昴 mǎo), the Quechua, the Japanese, the Maya, the Aztec, the Sioux, the Kiowa, and the Cherokee. In Hinduism, the Pleiades are known as Krittika and are associated with the war-god Kartikeya. They are also mentioned three times in the Bible

Galileo's drawings of the Pleiades star cluster from Sidereus Nuncius. Image courtesy of the History of Science Collections, University of Oklahoma Libraries.

The earliest known depiction of the Pleiades is likely a Northern German bronze age artifact known as the Nebra sky disk, dated to approximately 1600 BC. The Babylonian star catalogues name the Pleiades ^MULMUL (𒀯𒀯), meaning "stars" (literally "star star"), and they head the list of stars along the ecliptic, reflecting the fact that they were close to the point of vernal equinox around the 23rd century BC. The Ancient Egyptians may have used the names "Followers" and "Ennead" in the prognosis texts of the Calendar of Lucky and Unlucky Days of papyrus Cairo 86637. Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod's Works and Days, Homer's Iliad and Odyssey, and the Geoponica. Some scholars of Islam suggested that the Pleiades (ath-thurayya) are the "star" mentioned in Sura An-Najm ("The Star") of the Quran.

In Japan, the constellation is mentioned under the name Mutsuraboshi ("six stars") in the 8th century Kojiki. The constellation is now known in Japan as Subaru ("to unite"). It was chosen as the brand name of Subaru automobiles to reflect the origins of the firm as the joining of five companies, and is depicted in the firm's six-star logo.

Observational history

Galileo Galilei was the first astronomer to view the Pleiades through a telescope. He thereby discovered that the cluster contains many stars too dim to be seen with the naked eye. He published his observations, including a sketch of the Pleiades showing 36 stars, in his treatise Sidereus Nuncius in March 1610.

The Pleiades have long been known to be a physically related group of stars rather than any chance alignment. John Michell calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so surmised that the Pleiades and many other clusters of stars must be physically related. When studies were first made of the stars' proper motions, it was found that they are all moving in the same direction across the sky, at the same rate, further demonstrating that they were related.

Charles Messier measured the position of the cluster and included it as M45 in his catalogue of comet-like objects, published in 1771. Along with the Orion Nebula and the Praesepe cluster, Messier's inclusion of the Pleiades has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets—something that seems scarcely possible for the Pleiades. One possibility is that Messier simply wanted to have a larger catalogue than his scientific rival Lacaille, whose 1755 catalogue contained 42 objects, and so he added some bright, well-known objects to boost his list.

Edme-Sébastien Jeaurat then drew in 1782 a map of 64 stars of the Pleiades from his observations in 1779, which he published in 1786.

Distance

Location of Pleiades (circled)

The distance to the Pleiades can be used as an important first step to calibrate the cosmic distance ladder. As the cluster is so close to the Earth, its distance is relatively easy to measure and has been estimated by many methods. Accurate knowledge of the distance allows astronomers to plot a Hertzsprung-Russell diagram for the cluster, which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies, and a cosmic distance ladder can be constructed. Ultimately astronomers' understanding of the age and future evolution of the universe is influenced by their knowledge of the distance to the Pleiades. Yet some authors argue that the controversy over the distance to the Pleiades discussed below is a red herring, since the cosmic distance ladder can (presently) rely on a suite of other nearby clusters where consensus exists regarding the distances as established by Hipparcos and independent means (e.g., the Hyades, Coma Berenices cluster, etc.).

Measurements of the distance have elicited much controversy. Results prior to the launch of the Hipparcos satellite generally found that the Pleiades were about 135 parsecs away from Earth. Data from Hipparcos yielded a surprising result, namely a distance of only 118 parsecs by measuring the parallax of stars in the cluster—a technique that should yield the most direct and accurate results. Later work consistently argued that the Hipparcos distance measurement for the Pleiades was erroneous. In particular, distances derived to the cluster via the Hubble Space Telescope and infrared color-magnitude diagram fitting (so-called "spectroscopic parallax") favor a distance between 135 and 140 pc; a dynamical distance from optical interferometric observations of the Pleiad double Atlas favors a distance of 133–137 pc. However, the author of the 2007–2009 catalog of revised Hipparcos parallaxes reasserted that the distance to the Pleiades is ~120 pc and challenged the dissenting evidence. Recently, Francis and Anderson proposed that a systematic effect on Hipparcos parallax errors for stars in clusters biases calculation using the weighted mean and gave a Hipparcos parallax distance of 126 pc and photometric distance 132 pc based on stars in the AB Doradus, Tucana-Horologium, and Beta Pictoris moving groups, which are all similar in age and composition to the Pleiades. Those authors note that the difference between these results can be attributed to random error. More recent results using very-long-baseline interferometry (VLBI) (August 2014) and preliminary solutions using Gaia Data Release 1 (September 2016) and Gaia Data Release 2 (August 2018), determine distances of 136.2 ± 1.2 pc, 134 ± 6 pc 136.2 ± 5.0 pc, respectively. Although the Gaia Data Release 1 team was cautious about their result, the VLBI authors assert "that the Hipparcos measured distance to the Pleiades cluster is in error".

**Selected distance estimates to the Pleiades**
Year	Distance (pc)	Notes
1999	125	Hipparcos
2004	134.6 ± 3.1	Hubble Fine guidance sensor
2009	120.2 ± 1.9	Revised Hipparcos
2014	136.2 ± 1.2	Very-long-baseline interferometry
2016	134 ± 6	Gaia Data Release 1
2018	136.2 ± 5	Gaia Data Release 2

Composition

A map of the Pleiades

The cluster core radius is about 8 light years and tidal radius is about 43 light years. The cluster contains over 1,000 statistically confirmed members, although this figure excludes unresolved binary stars. Its light is dominated by young, hot blue stars, up to 14 of which can be seen with the naked eye depending on local observing conditions. The arrangement of the brightest stars is somewhat similar to Ursa Major and Ursa Minor. The total mass contained in the cluster is estimated to be about 800 solar masses and is dominated by fainter and redder stars.

The cluster contains many brown dwarfs, which are objects with less than about 8% of the Sun's mass, not heavy enough for nuclear fusion reactions to start in their cores and become proper stars. They may constitute up to 25% of the total population of the cluster, although they contribute less than 2% of the total mass. Astronomers have made great efforts to find and analyse brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.

Brightest stars

The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone, along with their parents Atlas and Pleione. As daughters of Atlas, the Hyades were sisters of the Pleiades. The English name of the cluster itself is of Greek origin (Πλειάδες), though of uncertain etymology. Suggested derivations include: from πλεῖν plein, "to sail", making the Pleiades the "sailing ones"; from πλέος pleos, "full, many"; or from πελειάδες peleiades, "flock of doves". The following table gives details of the brightest stars in the cluster:

**Pleiades bright stars**
Name	Pronunciation	Designation	Apparent magnitude	Stellar classification
Alcyone	/ælˈsaɪ.əni/ al-SY-ə-nee	Eta (25) Tauri	2.86	B7IIIe
Atlas	/ˈætləs/ AT-ləs	27 Tauri	3.62	B8III
Electra	/ɪˈlɛktrə/ i-LEK-trə	17 Tauri	3.70	B6IIIe
Maia	/ˈmeɪ.ə, ˈmaɪ.ə/ M(A)Y-ə	20 Tauri	3.86	B7III
Merope	/ˈmɛrəpi/ MERR-ə-pee	23 Tauri	4.17	B6IVev
Taygeta	/teɪˈɪdʒɪtə/ tay-IJ-i-tə	19 Tauri	4.29	B6V
Pleione	/ˈplaɪ.əni/ PLY-ə-nee	28 (BU) Tauri	5.09 (var.)	B8IVpe
Celaeno	/sɪˈliːnoʊ/ si-LEE-noh	16 Tauri	5.44	B7IV
Sterope, Asterope	/(ə)ˈstɛrəpi/ (ə)-STERR-ə-pee	21 and 22 Tauri	5.64;6.41	B8Ve/B9V
—	—	18 Tauri	5.66	B8V

Age and future evolution

Stars of Pleiades with color and 10,000 year backwards proper motion shown

Ages for star clusters can be estimated by comparing the Hertzsprung–Russell diagram for the cluster with theoretical models of stellar evolution. Using this technique, ages for the Pleiades of between 75 and 150 million years have been estimated. The wide spread in estimated ages is a result of uncertainties in stellar evolution models, which include factors such as convective overshoot, in which a convective zone within a star penetrates an otherwise non-convective zone, resulting in higher apparent ages.

Another way of estimating the age of the cluster is by looking at the lowest-mass objects. In normal main-sequence stars, lithium is rapidly destroyed in nuclear fusion reactions. Brown dwarfs can retain their lithium, however. Due to lithium's very low ignition temperature of 2.5 × 10⁶ K, the highest-mass brown dwarfs will burn it eventually, and so determining the highest mass of brown dwarfs still containing lithium in the cluster can give an idea of its age. Applying this technique to the Pleiades gives an age of about 115 million years.

The cluster is slowly moving in the direction of the feet of what is currently the constellation of Orion. Like most open clusters, the Pleiades will not stay gravitationally bound forever. Some component stars will be ejected after close encounters with other stars; others will be stripped by tidal gravitational fields. Calculations suggest that the cluster will take about 250 million years to disperse, with gravitational interactions with giant molecular clouds and the spiral arms of our galaxy also hastening its demise.

Reflection nebulosity

Hubble Space Telescope image of reflection nebulosity near Merope (IC 349)

With larger telescopes, the nebulosity around some of the stars can be easily seen; especially when long-exposure photographs are taken. Under ideal observing conditions, some hint of nebulosity around the cluster may even be seen with small telescopes or average binoculars. It is a reflection nebula, caused by dust reflecting the blue light of the hot, young stars.

It was formerly thought that the dust was left over from the formation of the cluster, but at the age of about 100 million years generally accepted for the cluster, almost all the dust originally present would have been dispersed by radiation pressure. Instead, it seems that the cluster is simply passing through a particularly dusty region of the interstellar medium.

Studies show that the dust responsible for the nebulosity is not uniformly distributed, but is concentrated mainly in two layers along the line of sight to the cluster. These layers may have been formed by deceleration due to radiation pressure as the dust has moved towards the stars.

Possible planets

Analyzing deep-infrared images obtained by the Spitzer Space Telescope and Gemini North telescope, astronomers discovered that one of the cluster's stars – HD 23514, which has a mass and luminosity a bit greater than that of the Sun, is surrounded by an extraordinary number of hot dust particles. This could be evidence for planet formation around HD 23514.