In the southern constellation of Phoenix lies SX Phoenicis. It’s a variable star that undergoes rapid physical changes we can measure directly from a suburban backyard.
What makes SX Phoenicis (SX Phe) particularly exciting for the backyard observer is its speed. While some variable stars take weeks, months, or even years to shift in brightness, SX Phe completes a full cycle in roughly 79 minutes! This short period allows us to witness an entire “heartbeat” of the star in a single observing session.
Unfortunately for observers in mid-to-high Northern latitudes, SX Phe sits low along the southern horizon, so it’s best viewed from lower latitudes. If you have a clear southern view, you can track the shift visually through binoculars, capture it in a sequence of DSLR exposures, or log it hands-free with a smart telescope.
The Quick Jump in Brightness
While the star takes about an hour to gradually dim, it snaps back from faint to bright in a steep 20-minute surge. In that brief window, the star more than doubles in brightness! If you stare at it alone, your eyes will easily miss the change because our night vision constantly self-adjusts. But if you anchor your view against a couple of nearby stars in the same field, that rapid climb becomes easier to notice.
My Observations
| Date | November 7, 2026 |
| Time | 8:46 p.m.–10:33 p.m. ET |
| Location | Tampa, FL |
| Instrument | Seestar S50 (Photometry Mode) |
| Exposure | 10.0s exposures |
| Seeing | Above Average |
| Transparency | Above Average |
The skies this weekend along the Florida west coast have been great, with moonless, clear skies. After all my years under the night sky, I decided I couldn’t pass up the opportunity to try tracking a variable star through photometric data.
At 8:46 p.m., I aimed the Seestar S50 toward the southern sky, switched it into photometry mode, and locked onto SX Phoenicis. For the next hour and 46 minutes, the Seestar S50 gathered 540 ten-second exposures until 10:33 p.m. I wanted to keep running the session, but SX Phe was dipping further into the distance haze.
SX Phe lingered near its faintest point, hovering in a dim trough around magnitude 7.68 to 7.78 until about 9:20 p.m. Then, right on cue, the numbers climbed. Over a 21-minute window between 9:21 p.m. and 9:42 p.m., the star’s magnitude increased, peaking at magnitude 6.76 (with a three-minute average around 6.92).
The CVS dataset is available here for download.
Key Stats
| Constellation | Phoenix |
| Object Type | SX Phoenicis pulsating variable |
| Best Viewing | Autumn |
| Visual Magnitude | +7.78 (trough) to +6.76 (peak) |
| Pulsation Period | ~79.2 minutes (0.055 days) |
| Rise Window | ~21 minutes |
| Spectral Type | A2 V – F0 |
| Designations | SX Phe, HD 223075, HIP 117254, CD-42 16565, SAO 231799 |
Sources and Notes
Banner photo by Wayne McGraw
Cohen, R. E., & Sarajedini, A. (2011). SX Phoenicis period-luminosity relations and the blue straggler connection. Monthly Notices of the Royal Astronomical Society, 419(1), 342–357. https://doi.org/10.1111/j.1365-2966.2011.19697.x
Handler, G., Guzik, J. A., & Bradley, P. A. (2009). Delta Scuti variables. AIP Conference Proceedings, 403–409. https://doi.org/10.1063/1.3246528
Xue, H.-F., & Niu, J.-S. (2020). DY Pegasi: An SX Phoenicis star in a binary system with an evolved companion. The Astrophysical Journal, 904(1), 5. https://doi.org/10.3847/1538-4357/abbc12