Reports - 2015
Astronomy Benalla Meeting Presentations - Wednesday 18th March 2015
Constellation of the Month - Aries Presenter: Patrick Watson
The night started by posing the question “What Year is It?”
As it turned out the answer sought was -The Chinese Lunar New Year - the Year of the Goat.
There was Capricornus - commonly represented in the form of a sea-goat: a mythical creature that is half goat, half
fish. Not a real goat! The nearest to be chosen was Aries - Latin for ram. Not a goat but a cloven foot animal never the
less.
Aries carries with it an association with The First Point of Aries, the location of the Vernal Equinox.
The First Point of Aries is so called because, when Hipparchus defined it in 130 BCE, it was located in the eastern
extreme of the constellation of Aries as seen in the time-simulation picture, below. The First Point of Aries is
considered to be at the celestial "prime meridian" from which right ascensions are calculated.
130BC
Because of precession, the vernal quinox is now found in the constellation Pisces, as seen in the next picture.
2015
The star Gamma Arietis (γ Ari, γ Arietis) at Mv 3.8 is in fact a binary system. It has the traditional name Mesarthim, of
obscure origin, and has been called "the First Star in Aries" as having been (at one time) the nearest visible star to
the equinoctial point - see below.
The asterism which is intended to indicate the Ram is shown below:
- and includes the stars Hamel (alpha Arietis), Sheratan (beta Arietis) and Mesatharim.
The few deep-sky objects in Aries are very dim. Two supernova (SN 2003hl & SN 2003iq) have appeared in the spiral
galaxy NGC 772 - imaged below:
Also shown is asteroid 6223 Dahl - named in honour of the Welsh-born author Roald Dahl (b. 1916 d. 1990). His
Willy Wonka and the Chocolate Factory and James and the Giant Peach are classics of children's literature.
There are a number of meteor showers (generally - the Arietids) throughout the year which emante from Aries.
Aries contains several stars with extrasolar planets including HIP 14810, a G5 star, which is orbited by three giant
planets (those more than ten times the mass of Earth).
Other objects of interest include:
Teegarden's Star, an M-type brown dwarf ilocated about 12 light years from the Solar System. This star was found to
have a very large proper motion of about 5 arcseconds per year. Only seven stars with such large proper motions are
currently known.
53 Arietis - a runaway star. A runaway star is one which is moving through space with an abnormally high velocity
relative to the surrounding interstellar medium. In the most favoured explanation scenario, it is thought that a
supernova explosion occured in multiple star system which results the components moving away at high speed.
This is believed to be the case where AE Aurigae, Mu Columbae and 53 Arietis are all moving away from each other
at velocities of over 100 km/s (for comparison, the Sun moves through the galaxy at about 20 km/s faster than
[relative to] the local average).
Tracing their motions back, their paths intersect near to the Orion Nebula about 2 million years ago. See below the
current positions (the constellations) of these three stars relative to Orion.
An emission nebula in the constellation of Orion, Barnard's Loop (below) is believed to be the remnant of the
supernova that ejected these stars.
Images:
Simulation Curriculum Corproration: Starry Night Pro Plus
Wikipedia
NASA
fish. Not a real goat! The nearest to be chosen was Aries - Latin for ram. Not a goat but a cloven foot animal never the
less.
Aries carries with it an association with The First Point of Aries, the location of the Vernal Equinox.
The First Point of Aries is so called because, when Hipparchus defined it in 130 BCE, it was located in the eastern
extreme of the constellation of Aries as seen in the time-simulation picture, below. The First Point of Aries is
considered to be at the celestial "prime meridian" from which right ascensions are calculated.
130BC
Because of precession, the vernal quinox is now found in the constellation Pisces, as seen in the next picture.
2015
The star Gamma Arietis (γ Ari, γ Arietis) at Mv 3.8 is in fact a binary system. It has the traditional name Mesarthim, of
obscure origin, and has been called "the First Star in Aries" as having been (at one time) the nearest visible star to
the equinoctial point - see below.
The asterism which is intended to indicate the Ram is shown below:
- and includes the stars Hamel (alpha Arietis), Sheratan (beta Arietis) and Mesatharim.
The few deep-sky objects in Aries are very dim. Two supernova (SN 2003hl & SN 2003iq) have appeared in the spiral
galaxy NGC 772 - imaged below:
Also shown is asteroid 6223 Dahl - named in honour of the Welsh-born author Roald Dahl (b. 1916 d. 1990). His
Willy Wonka and the Chocolate Factory and James and the Giant Peach are classics of children's literature.
There are a number of meteor showers (generally - the Arietids) throughout the year which emante from Aries.
Aries contains several stars with extrasolar planets including HIP 14810, a G5 star, which is orbited by three giant
planets (those more than ten times the mass of Earth).
Other objects of interest include:
Teegarden's Star, an M-type brown dwarf ilocated about 12 light years from the Solar System. This star was found to
have a very large proper motion of about 5 arcseconds per year. Only seven stars with such large proper motions are
currently known.
53 Arietis - a runaway star. A runaway star is one which is moving through space with an abnormally high velocity
relative to the surrounding interstellar medium. In the most favoured explanation scenario, it is thought that a
supernova explosion occured in multiple star system which results the components moving away at high speed.
This is believed to be the case where AE Aurigae, Mu Columbae and 53 Arietis are all moving away from each other
at velocities of over 100 km/s (for comparison, the Sun moves through the galaxy at about 20 km/s faster than
[relative to] the local average).
Tracing their motions back, their paths intersect near to the Orion Nebula about 2 million years ago. See below the
current positions (the constellations) of these three stars relative to Orion.
An emission nebula in the constellation of Orion, Barnard's Loop (below) is believed to be the remnant of the
supernova that ejected these stars.
Images:
Simulation Curriculum Corproration: Starry Night Pro Plus
Wikipedia
NASA
