Stars German cartographer
Johann Bayer used the Greek letters
alpha through
nu to label the most prominent stars in the constellation. English astronomer
John Flamsteed observed and labelled two stars each as
delta,
epsilon,
zeta and nu. He added
pi and
rho, not using
xi and
omicron as Bayer used these letters to denote Cygnus and Hercules on his map. The brightest star in the constellation is Vega (Alpha Lyrae), a
main-sequence star of
spectral type A0Va. Only 7.7 parsecs distant, Vega is a
Delta Scuti variable, varying between
magnitudes −0.02 and 0.07 over 0.2 days. On average, it is the second-brightest star of the northern hemisphere (after
Arcturus) and the fifth-brightest star in all, surpassed only by Arcturus,
Alpha Centauri,
Canopus, and
Sirius. Vega was the
pole star in the year 12,000 BCE, and will again become the pole star around 14,000 CE. Vega is one of the most magnificent of all stars, and has been called "arguably the next most important star in the sky after the
Sun". Vega was the first star other than the Sun to be
photographed, as well as the first to have a clear
spectrum recorded, showing
absorption lines for the first time. The star was the first single main-sequence star other than the Sun to be known to emit
X-rays, and is surrounded by a circumstellar
debris disk, similar to the
Kuiper Belt. Vega forms one corner of the famous
Summer Triangle asterism; along with
Altair and
Deneb, these three stars form a prominent triangle during the northern hemisphere summer. Vega also forms one vertex of a much smaller triangle, along with Epsilon and
Zeta Lyrae. Zeta forms a wide
binary star visible in binoculars, consisting of an
Am star and an
F-type subgiant. The Am star has an additional close companion, bringing the total number of stars in the system to three. Both components are themselves close binaries which can be seen with telescopes to consist of
A- and F-type stars, and a faint star was recently found to orbit component C as well, for a total of five stars. with a dominant period of 79 days, while the fainter
Delta1 Lyrae is a
spectroscopic binary consisting of a
B-type primary and an unknown secondary. Both systems, however, have very similar
radial velocities, and are the two brightest members of a sparse open cluster known as the
Delta Lyrae cluster. South of Delta is Sulafat (
Gamma Lyrae), a
blue giant and the second-brightest star in the constellation. Around 190 parsecs distant, The final star forming the lyre's figure is Sheliak (
Beta Lyrae), also a binary composed of a blue bright giant and an early B-type star. In this case, the stars are so close together that the larger giant is overflowing its
Roche lobe and transferring material to the secondary, forming a
semidetached system. The secondary, originally the less massive of the two, has accreted so much mass that it is now substantially more massive, albeit smaller, than the primary, and is surrounded by a thick
accretion disk. The plane of the orbit is aligned with Earth and the system thus shows
eclipses, dropping nearly a full magnitude from its 3rd-magnitude baseline every 13 days, although its period is increasing by around 19 seconds per year. It is the prototype of the
Beta Lyrae variables, eclipsing semidetached binaries of early spectral types in which there are no exact onsets of eclipses, but rather continuous changes in brightness. Another easy-to-spot variable is the bright
R Lyrae, north of the main asterism. Also known as 13 Lyrae, it is a 4th-magnitude
red giant semiregular variable that varies by several tenths of a magnitude. Its periodicity is complex, with several different periods of varying lengths, most notably one of 46 days and one of 64 days. Even further north is
FL Lyrae, a much fainter 9th-magnitude
Algol variable that drops by half a magnitude every 2.18 days during the primary eclipse. Both components are main-sequence stars, the primary being late F-type and the secondary late
G-type. The system was one of the first main-sequence eclipsing binaries containing G-type star to have its properties known as well as the better-studied early-type eclipsing binaries. At the very northernmost edge of the constellation is the even fainter
V361 Lyrae, an eclipsing binary that does not easily fall into one of the traditional classes, with features of Beta Lyrae,
W Ursae Majoris, and
cataclysmic variables. It may be a representative of a very brief phase in which the system is transitioning into a
contact binary. It can be found less than a degree away from the naked-eye star
16 Lyrae, a 5th-magnitude
A-type subgiant around 73 parsecs distant.
Lambda Lyrae, and
HD 173780. Also nearby is the faint
HP Lyrae, a
post-asymptotic giant branch (AGB) star that shows variability. The reason for its variability is still a mystery: first cataloged as an eclipsing binary, it was theorized to be an
RV Tauri variable in 2002, but if so, it would be by far the hottest such variable discovered. In the extreme east is
RR Lyrae, the prototype of the large class of variables known as
RR Lyrae variables, which are pulsating variables similar to
Cepheids, but are evolved
population II stars of spectral types A and F. Such stars are usually not found in a galaxy's
thin disk, but rather in the
galactic halo. Such stars serve as
standard candles, and thus are a reliable way to calculate distances to the globular clusters in which they reside. The easternmost star designated by
Flamsteed,
19 Lyrae, is also a small-amplitude variable, an
Alpha2 Canum Venaticorum variable with a period of just over one day. Another evolved star is the naked-eye variable
XY Lyrae, a red bright giant Also just visible to the naked eye is the peculiar
classical Cepheid V473 Lyrae. It is unique in that it is the only known Cepheid in the
Milky Way to undergo periodic phase and amplitude changes, analogous to the Blazhko effect in RR Lyrae stars. At 1.5 days, its period was the shortest known for a classical Cepheid at the time of its discovery.
W and
S Lyrae are two of the many
Mira variables in Lyra. W varies between 7th and 12th magnitudes over approximately 200 days, while S, slightly fainter, is a silicate
carbon star, likely of the
J-type. Another evolved star is
EP Lyrae, a faint RV Tauri variable and an "extreme example" of a post-AGB star. It and a likely companion are surrounded by a circumstellar disk of material. Rather close to Earth at a distance of only is
Gliese 758. The sunlike primary star has a
brown dwarf companion, the coldest to have been imaged around a sunlike star in thermal light when it was discovered in 2009. Only slightly farther away is
V478 Lyrae, an eclipsing
RS Canum Venaticorum variable whose primary star shows active
starspot activity. One of the most peculiar systems in Lyra is
MV Lyrae, a
nova-like star consisting of a
red dwarf and a
white dwarf. Originally classified as a
VY Sculptoris star due to spending most time at maximum brightness, since around 1979 the system has been dominantly at minimum brightness, with periodic outbursts. Its nature is still not fully understood. Another outbursting star is
AY Lyrae, an
SU Ursae Majoris-type
dwarf nova that has undergone several
superoutbursts. Of the same type is
V344 Lyrae, notable for an extremely short period between superoutbursts coupled with one of the highest amplitudes for such a period. The true
nova HR Lyrae flared in 1919 to a maximum magnitude of 6.5, over 9.5 magnitudes higher than in quiescence. Some of its characteristics are similar to those of
recurring novae.
Deep-sky objects is composed of a large number of stars, tightly bound to each other by gravity. In Lyra are the objects M56, M57, and Kuiper 90.
M56 is a rather loose
globular cluster at a distance of approximately 32,900
light-years, with a diameter of about 85 light-years. Its apparent brightness is 8.3m.
M57, also known as the "Ring Nebula" and NGC 6720, at a distance of 2,550 light-years from Earth is one of the best known
planetary nebulae and the second to be discovered; its integrated magnitude is 8.8. It can be found halfway between
Gamma Lyrae and Beta Lyrae. Another planetary nebula in Lyra is
Abell 46. The central star,
V477 Lyrae, is an eclipsing
post-common-envelope binary, consisting of a white dwarf primary and an oversized secondary component due to recent accretion. The nebula itself is of relatively low surface brightness compared to the central star, and is undersized for the primary's mass for reasons not yet fully understood. NGC 6791 is a cluster of stars in Lyra. It contains three age groups of stars: 4 billion year-old white dwarfs, 6 billion year-old white dwarfs and 8 billion year-old normal stars.
NGC 6745 is an irregular
spiral galaxy in Lyra that is at a distance of 208 million light-years. Several million years ago, it
collided with a smaller galaxy, which created a region filled with young, hot, blue stars. Astronomers do not know if the collision was simply a glancing blow or a prelude to a full-on merger, which would end with the two galaxies incorporated into one larger, probably
elliptical galaxy. and unable to be completely explained by known phenomena. The light curve observed over the next 100 days was consistent with that of a
supernova or even a
hypernova, dubbed
SN 2005nc. The host galaxy proved elusive to find at first, although it was subsequently identified.
Exoplanets In orbit around the orange subgiant star
HD 177830 is one of the earliest
exoplanets to be detected. A jovian-mass planet, it orbits in an eccentric orbit with a period of 390 days. A second planet closer to the star was discovered in 2011. Visible to the naked eye are
HD 173416, a
yellow giant hosting a planet over twice the mass of Jupiter discovered in 2009; and
HD 176051, a low-mass binary star containing another high-mass planet. Just short of naked-eye visibility is
HD 178911, a triple system consisting of a close binary and a visually separable sunlike star. The sunlike star has a planet with over 6 Jupiter masses discovered in 2001, the second found in a triple system after that of
16 Cygni. One of the most-studied exoplanets in the night sky is
TrES-1b, in orbit around the star
GSC 02652-01324. Detected from a
transit of its parent star, the planet has around 3/4 the mass of Jupiter, yet orbits its parent star in only three days. The transits have been reported to have anomalies multiple times. Originally thought to be possibly due to the presence of an Earth-like planet, it is now accepted that the irregularities are due to a large starspot. Also discovered by the transit method is
WASP-3b, with 1.75 times the mass of Jupiter. At the time of its discovery, it was one of the hottest known exoplanets, in orbit around the
F-type main-sequence star WASP-3. Similar to TrES-1b, irregularities in the transits had left open the possibility of a second planet, although this now appears unlikely as well. Lyra is one of three constellations (along with neighboring Cygnus and Draco) to be in the
Kepler Mission's field of view, and as such it contains many more known exoplanets than most constellations. One of the first discovered by the mission is
Kepler-7b, an extremely low-density exoplanet with less than half the mass of Jupiter, yet nearly 1.5 times the radius. Almost as sparse is
Kepler-8b, only slightly more massive and of a similar radius. The
Kepler-20 system contains five known planets; three of them are only slightly smaller than
Neptune, while the other two are some of the first
Earth-sized exoplanets to be discovered.
Kepler-37 is another star with an exoplanet discovered by Kepler; the planet is the smallest known
extrasolar planet known as of February 2013. In April 2013, it was announced that of the five planets orbiting
Kepler-62, at least two—
Kepler-62e and
Kepler-62f—are within the boundaries of the
habitable zone of that star, where scientists think liquid water could exist, and are both candidates for being a solid, rocky, earth-like planet. The
exoplanets are 1.6 and 1.4 times the diameter of
Earth respectively, ==See also==