Stars Bayer gave the most prominent stars
Bayer designations Alpha through Tau. Later designated three stars as Rho and two stars as Gamma, Theta, and Tau. Theta Arietis was dropped because it felt it was too dim, leaving Theta as the sole Theta. c Arietis was included in some atlases which is the star c Muscae Borealis in the obsolete constellation
Musca Borealis, which is now an asterism.
Bright stars Aries has three prominent stars forming an
asterism, designated Alpha, Beta, and Gamma Arietis by
Johann Bayer. Alpha (Hamal) and Beta (Sheratan) are commonly used for navigation. There is also one other star above the fourth magnitude, 41 Arietis (Bharani) is a similar star of magnitude 4.51, 172 light-years away. Its spectral class is K1 and its absolute magnitude is 0.0.
35 Arietis is a dim star of magnitude 4.55, 343 light-years away. Its spectral class is B3 and its absolute magnitude is −1.7.
41 Arietis, known both as c Arietis and Nair al Butain, is a brighter star of magnitude 3.63, 165 light-years away. Its spectral class is B8 and it has a luminosity of . Its absolute magnitude is −0.2.
53 Arietis is a
runaway star of magnitude 6.09, 815 light-years away. Its spectral class is B2. It was likely ejected from the
Orion Nebula approximately five million years ago, possibly due to
supernovae. Finally,
Teegarden's Star is the closest star to Earth in Aries. It is a
red dwarf of magnitude 15.14 and spectral class M6.5V. With a proper motion of 5.1 arcseconds per year, it is the 24th closest star to Earth overall.
Variable stars Aries has its share of variable stars, including R and U Arietis, Mira-type variable stars, and T Arietis, a semi-regular variable star.
R Arietis is a
Mira variable star that ranges in magnitude from a minimum of 13.7 to a maximum of 7.4 with a period of 186.8 days. It is 4,080 light-years away.
U Arietis is another Mira variable star that ranges in magnitude from a minimum of 15.2 to a maximum of 7.2 with a period of 371.1 days.
T Arietis is a
semiregular variable star that ranges in magnitude from a minimum of 11.3 to a maximum of 7.5 with a period of 317 days. It is 1,630 light-years away. One particularly interesting variable in Aries is
SX Arietis, a rotating variable star considered to be the prototype of its class,
helium variable stars. SX Arietis stars have very prominent emission lines of Helium I and Silicon III. They are normally main-sequence B0p—B9p stars, and their variations are not usually visible to the naked eye. Therefore, they are observed photometrically, usually having periods that fit in the course of one night. Similar to
α2s, SX Arietis stars have periodic changes in their light and magnetic field, which correspond to the periodic rotation; they differ from the α2 Canum Venaticorum variables in their higher temperature. There are between 39 and 49 SX Arietis variable stars currently known; ten are noted as being "uncertain" in the
General Catalog of Variable Stars.
Deep sky objects NGC 772 is a
spiral galaxy with an
integrated magnitude of 10.3, located southeast of β Arietis and 15 arcminutes west of
15 Arietis. It is a relatively bright galaxy and shows obvious nebulosity and ellipticity in an amateur telescope. It is 7.2 by 4.2 arcminutes, meaning that its
surface brightness, magnitude 13.6, is significantly lower than its integrated magnitude. NGC 772 is a
class SA(s)b galaxy, which means that it is an unbarred spiral galaxy without a ring that possesses a somewhat prominent
bulge and spiral arms that are wound somewhat tightly. The main arm, on the northwest side of the galaxy, is home to many
star forming regions; this is due to previous
gravitational interactions with other galaxies. NGC 772 has a small companion galaxy,
NGC 770, that is about 113,000 light-years away from the larger galaxy. The two galaxies together are also classified as Arp 78 in the
Arp peculiar galaxy catalog. NGC 772 has a diameter of 240,000 light-years and the system is 114 million light-years from Earth. Another spiral galaxy in Aries is
NGC 673, a face-on class SAB(s)c galaxy. It is a weakly
barred spiral galaxy with loosely wound arms. It has no ring and a faint bulge and is 2.5 by 1.9 arcminutes. It has two primary arms with fragments located farther from the core. 171,000 light-years in diameter, NGC 673 is 235 million light-years from Earth.
NGC 678 and
NGC 680 are a pair of galaxies in Aries that are only about 200,000 light-years apart. Part of the
NGC 691 group of galaxies, both are at a distance of approximately 130 million light-years. NGC 678 is an edge-on spiral galaxy that is 4.5 by 0.8 arcminutes. NGC 680, an
elliptical galaxy with an asymmetrical boundary, is the brighter of the two at magnitude 12.9; NGC 678 has a magnitude of 13.35. Both galaxies have bright cores, but NGC 678 is the larger galaxy at a diameter of 171,000 light-years; NGC 680 has a diameter of 72,000 light-years. NGC 678 is further distinguished by its prominent
dust lane. NGC 691 itself is a spiral galaxy slightly inclined to our line of sight. It has multiple spiral arms and a bright core. Because it is so diffuse, it has a low surface brightness. It has a diameter of 126,000 light-years and is 124 million light-years away.
NGC 877 is the brightest member of an 8-galaxy group that also includes NGC 870, NGC 871, and NGC 876, with a magnitude of 12.53. It is 2.4 by 1.8 arcminutes and is 178 million light-years away with a diameter of 124,000 light-years. Its companion is NGC 876, which is about 103,000 light-years from the core of NGC 877. They are interacting gravitationally, as they are connected by a faint stream of gas and dust.
Arp 276 is a different pair of interacting galaxies in Aries, consisting of NGC 935 and IC 1801. NGC 821 is an E6 elliptical galaxy. It is unusual because it has hints of an early spiral structure, which is normally only found in
lenticular and spiral galaxies. NGC 821 is 2.6 by 2.0 arcminutes and has a visual magnitude of 11.3. Its diameter is 61,000 light-years and it is 80 million light-years away. Another unusual galaxy in Aries is
Segue 2, a
dwarf and
satellite galaxy of the Milky Way, recently discovered to be a potential relic of the
epoch of reionization.
Meteor showers Aries is home to several
meteor showers. The
Daytime Arietid meteor shower is one of the strongest meteor showers that occurs during the day, lasting from 22 May to 2 July. It is an annual shower associated with the Marsden group of
comets that peaks on 7 June with a maximum
zenithal hourly rate of 54 meteors. Its parent body may be the asteroid
Icarus. The meteors are sometimes visible before dawn, because the
radiant is 32 degrees away from the Sun. They usually appear at a rate of 1–2 per hour as "earthgrazers", meteors that last several seconds and often begin at the horizon. Because most of the Daytime Arietids are not visible to the naked eye, they are observed in the
radio spectrum. This is possible because of the ionized gas they leave in their wake. Other meteor showers radiate from Aries during the day; these include the Daytime Epsilon Arietids and the Northern and Southern Daytime May Arietids. The
Jodrell Bank Observatory discovered the Daytime Arietids in 1947 when James Hey and G. S. Stewart adapted the
World War II-era radar systems for meteor observations. The
Delta Arietids are another meteor shower radiating from Aries. Peaking on 9 December with a low peak rate, the shower lasts from 8 December to 14 January, with the highest rates visible from 8 to 14 December. The average Delta Arietid meteor is very slow, with an average velocity of per second. However, this shower sometimes produces bright
fireballs. This meteor shower has northern and southern components, both of which are likely associated with
1990 HA, a
near-Earth asteroid. The
Autumn Arietids also radiate from Aries. The shower lasts from 7 September to 27 October and peaks on 9 October. Its peak rate is low. The
Epsilon Arietids appear from 12 to 23 October. Other meteor showers radiating from Aries include the October Delta Arietids,
Daytime Epsilon Arietids,
Daytime May Arietids,
Sigma Arietids,
Nu Arietids, and
Beta Arietids. The Sigma Arietids, a class IV meteor shower, are visible from 12 to 19 October, with a maximum zenithal hourly rate of less than two meteors per hour on 19 October.
Planetary systems Aries contains several stars with
extrasolar planets.
HIP 14810, a G5 type star, is orbited by three
giant planets (those more than ten times the
mass of Earth).
HD 12661, like HIP 14810, is a G-type main sequence star, slightly larger than the Sun, with two orbiting planets. One planet is 2.3 times the mass of Jupiter, and the other is 1.57 times the mass of Jupiter.
HD 20367 is a G0 type star, approximately the size of the Sun, with one orbiting planet. The planet, discovered in 2002, has a mass 1.07 times that of Jupiter and orbits every 500 days. In 2019, scientists conducting the CARMENES survey at the
Calar Alto Observatory announced evidence of two
Earth-mass exoplanets orbiting
Teegarden's star, located in Aries, within its
habitable zone. The star is a small
red dwarf with only around a tenth of the mass and radius of the Sun. It has a large
radial velocity.{{cite journal | display-authors=1 | last1=Tanner | first1=Angelle | last2=White | first2=Russel | last3=Bailey | first3=John | last4=Blake | first4=Cullen | last5=Blake | first5=Geoffrey | last6=Cruz | first6=Kelle | last7=Burgasser | first7=Adam J. | last8=Kraus | first8=Adam | title=Keck NIRSPEC Radial Velocity Observations of Late-M Dwarfs | journal=The Astrophysical Journal Supplement | volume=203 | issue=1 | pages=7 | date=November 2012 | doi=10.1088/0067-0049/203/1/10 | bibcode=2012ApJS..203...10T == See also ==