Starship Asterisk*

Joules wrote:I wonder if the Hale telescope could have matched this back in the day, had it been in the proper hemisphere.
Pretty good imagery for any telescope, far less a 32 incher.

ta152h0 wrote:loiwer right, 3/4 way a double spike. two stars really close ?

On the sky this field of view spans about 1 degree. That corresponds to almost 9 light-years at the estimated distance of the nearby star forming region.

JuanAustin wrote:I am taking a trip to Sydney at the end of March and will be my first trip south of the equator. I would dearly love to do some stargazing while down under, does anyone have any recommendations to engage someone somewhere somehow? Thanks!

geckzilla wrote:

ta152h0 wrote:loiwer right, 3/4 way a double spike. two stars really close ?

Only apparently, it seems. The two have vastly different parallaxes. The one on the right, HD 176269, has a parallax of 23.39 mas. The one on the left, HD 176270, only has a parallax of 4.26 mas. So it would seem the one on the right is significantly closer to us.
http://simbad.u-strasbg.fr/simbad/sim-i ... =HD+176269
http://simbad.u-strasbg.fr/simbad/sim-i ... =HD+176270

Ann wrote: I'd say we are most definitely talking about a double star, for the following reasons:

1) It would be absolutely extremely unlikely for two stars of such similar colors and magnitudes to be so close together in the sky if they were not physically related. Given the fact that both stars are also blue, which is a much rarer color among 6th to 7th magnitude stars than yellow, makes it even more unlikely that they are not related.

2) The simple fact that these two stars are blue means that they are also (fairly) massive. Massive stars are particularly likely to form binaries. Even though this paper refers to much more massive stars than HD 176270 and HD 176269, it still suggests that binarity is a quite common phenomenon among early A- and late B-type stars like HD 176270 and HD 176269.

3) If these stars are really a (very wide) pair, but extremely close together on the sky, the Hipparcos parallaxes measured by the Hipparcos satellite are likely to go haywire. In other words, they are not reliable at all. Therefore, the Hipparcos parallax of HD 176269 on the right is 23.39 ± 6.47 mas. That is a high degree of uncertainty. The Hipparcos parallax of HD 176270 on the left is 4.26 ± 4.38 mas. So if we are talking about signal to noise here, the noise is worse than the signal. The proper motion in RA is equally uncertain for HD 176270, 6.03 ± 7.44 mas. For HD 176269, it is 16.05 ± 10.63 mas. So Hipparcos parallaxes and proper motion measurements are pretty useless here.

4) Finally, HD 176269 and 176270 are the brightest stars of an active but low-mass region of star formation. That the most massive stars formed in such a region of star formation would be early A- and late B-type stars like HD 176269 and 176270 is exactly what we should expect.

HD 176270 and 176269 are definitely a pair.

Ann

ta152h0 wrote:do binary stars exhibit two spikes ? and such spikes, if they exist can reveal a distance in two dimensions ?

geckzilla wrote:I think you have a good argument that the young stars both formed recently in the same stellar nursery even though that is not explicitly the point you are trying to make. I still unconvinced that they are gravitationally bound.

A.11. CrA-11 (HD 176269, HR 7169)

CrA-11, more commonly known as HD 176269, is an optically detected PMS star with a spectral type of B8V that was first observed by Knacke et al. (1973) as HR 7169 to be a possible member of the young stellar association near R CrA (~12' to the SW). Another B8V star ~12'' away, HR 7170 (HD 176270), was also listed as a possible member and we include it in Table 7. These two sources were detected, but not spatially resolved, by the IRAS (IRAS 18; Wilking et al. 1992) and EINSTEIN satellites (CrAPMS 10; Walter et al. 1997).

HD 176269 was observed in the near-infrared by Glass & Penston (1975) and is referred to in their Table 1 as source l; HD 176270 was also observed, and is listed as source k. Later, Patten (1998) does not classify the HD 176269/HD 176270 pair (which he calls source R05) as a likely association member: he finds a spectral type of B9V for the source and detects a ROSAT X-ray counterpart, however the source does not fulfill enough criteria for him to consider it an association member. Note that these stars are far enough afield so that they were not included as part of the Forbrich & Preibisch (2007) Chandra study.

HD 176269 was also detected with ISOCAM by O99, and is referred to as ISO-CrA 110 in their survey. ISO-CrA 110 was found to have a mid-infrared excess based on those observations so it is considered one of their YSO candidates. HD 176270 is referred to as ISO-CrA 111 in the same study, and it was not found to have a mid-infrared excess.

These studies are consistent with the Spitzer observations; we classify HD 176269 as a Class III based on the shape of its SED. Although we do not classify HD 176270 as a YSO candidate, it very likely is also a Class III based on its colors and SED shape (see Table 7). The SEDs of the two stars look similar out to 8 μm. However, at 24 μm, HD 176269 is much brighter than HD 176270. Neither source is detected at 70 μm.

geckzilla wrote:Well, it may be deserved, but from this outsider's viewpoint it is also worth noting that you appear to have an ax to grind with the Hipparcos catalog which makes you prone to wanting it to be wrong.

You may be interested in a couple of paragraphs from this paper specifically devoted to these two stars. There are uncertainties about them because no one has given them a really good look more recently other than that 2007 Hipparcos reduction (at least as far as I can find).

A.11. CrA-11 (HD 176269, HR 7169)

CrA-11, more commonly known as HD 176269, is an optically detected PMS star with a spectral type of B8V that was first observed by Knacke et al. (1973) as HR 7169 to be a possible member of the young stellar association near R CrA (~12' to the SW). Another B8V star ~12'' away, HR 7170 (HD 176270), was also listed as a possible member and we include it in Table 7. These two sources were detected, but not spatially resolved, by the IRAS (IRAS 18; Wilking et al. 1992) and EINSTEIN satellites (CrAPMS 10; Walter et al. 1997).

HD 176269 was observed in the near-infrared by Glass & Penston (1975) and is referred to in their Table 1 as source l; HD 176270 was also observed, and is listed as source k. Later, Patten (1998) does not classify the HD 176269/HD 176270 pair (which he calls source R05) as a likely association member: he finds a spectral type of B9V for the source and detects a ROSAT X-ray counterpart, however the source does not fulfill enough criteria for him to consider it an association member. Note that these stars are far enough afield so that they were not included as part of the Forbrich & Preibisch (2007) Chandra study.

HD 176269 was also detected with ISOCAM by O99, and is referred to as ISO-CrA 110 in their survey. ISO-CrA 110 was found to have a mid-infrared excess based on those observations so it is considered one of their YSO candidates. HD 176270 is referred to as ISO-CrA 111 in the same study, and it was not found to have a mid-infrared excess.

These studies are consistent with the Spitzer observations; we classify HD 176269 as a Class III based on the shape of its SED. Although we do not classify HD 176270 as a YSO candidate, it very likely is also a Class III based on its colors and SED shape (see Table 7). The SEDs of the two stars look similar out to 8 μm. However, at 24 μm, HD 176269 is much brighter than HD 176270. Neither source is detected at 70 μm.